Maturation and conversion of somatic embryos are two crucial steps that hamper the development of efficient somatic embryogenesis systems in olive. Herein, a simple and efficient protocol for the maturation and conversion of olive somatic embryos is reported. Globular somatic embryos derived from seeds of cv. Dahbia were cultured on either half-strength olive (OM) or olive cyclic embryogenesis (ECO) media, with and without plant growth regulators (PGRs). The embryos reached the cotyledonary stage in 9 weeks, but those cultured on ECO medium containing 0.1 mg·L⁻¹ 6-(dimethylallylamino)purine (2iP), 0.1 mg·L⁻¹ 6-benzyladenine (BA) and 0.05 mg·L⁻¹ indole-3-butyric acid (IBA) exhibited the largest sizes, with an average of 4.7 mm. Somatic embryo conversion into plantlets was evaluated using different culture media (half-strength OM or one-third strength Murashige and Skoog (MS)), light conditions (light or dark) and desiccation pretreatments. The highest rate of somatic embryo conversion (45%) was observed under a 16 h photoperiod on half strength OM medium containing 0.1 mg·L⁻¹ gibberellic acid (GA₃) and 0.1 mg·L⁻¹ 1-naphthalene acetic acid (NAA). The embryos that failed to germinate showed either necrosis, cotyledon greening with no further conversion, adventitious bud formation or secondary embryogenesis. The findings of this study will be beneficial for biotechnological applications in olive.

Caper (Capparis spinosa L.) is a shrubby plant species recalcitrant to vegetative propagation and generally difficult to propagate by seeds. This is due to the difficulties associated with seed germination, root induction from stem cuttings, and plant hardening. Propagation by tissue culture would be a good alternative and promising approach to overcome the limitations of conventional propagation. Tissue culture methods can be used for the clonal propagation of caper plants. Indeed, in many plant species, micropropagation has played a decisive role in the rapid and large-scale production of uniform and genetically stable plants. Tissue culture methods can also be used in genetic improvement and conservation programs. In this review, we first provided an overview on caper and its conventional means of propagation, then we described the different methods of caper micropropagation, i.e., in vitro seed germination and seedling development, propagation by nodal segmentation of elongated shoots (i.e., microcuttings), and adventitious organogenesis. These micropropagation methods can make it possible to overcome all the obstacles preventing large-scale propagation and genetic improvement of caper. Thus, the most updated information on the progress made in the field of caper micropropagation is reported and future perspectives are outlined.

Maturation and germination of somatic embryos are two crucial steps in the somatic embryogenesis process. Herein, we evaluated the effects of several factors on the maturation and germination of date palm somatic embryos. Globular somatic embryos of cv. ‘Najda’ were cultured on Murashige and Skoog medium at full strength (MS), half strength (1/2MS), and one-third strength (1/3MS), with or without agar, and supplemented with various concentrations of mannitol, sorbitol, polyethylene glycol (PEG, MW 8000) and abscisic acid (ABA). Our results showed that culture medium strength and texture (liquid or semi-solid), osmotic agents, and the concentration and time of exposure to ABA influence somatic embryo maturation. The highest mean number of mature somatic embryos (106.4 per 100 mg fresh weight callus) was obtained after 3 weeks of culture on full-strength liquid MS medium supplemented with 30 g L-1 PEG and 40 µM ABA, followed by 9 weeks of culture on the same medium but without ABA. Somatic embryo germination was achieved by transferring mature embryos to MS medium containing various combinations of 1-naphthalene acetic acid (NAA), 6-benzylaminopurine (BAP) and gibberellic acid (GA3). The highest germination rate (68%) of somatic embryos occurred in the presence of 0.5 mg L-1 NAA. However, there was no significant difference with the other germination media (54-66%). Plantlet acclimatization was successfully accomplished, and the survival rate was 80% after 6 months in the glasshouse. The findings of the present study open new prospects for massive propagation of this bayoud-resistant date palm cultivar.

As part of the search for biochemical markers of somatic embryogenesis in tissue cultures of olive (Olea europaea L.), peroxidases (POXs) in both the soluble and ionically wall-bound fractions were studied in two reputed olive cultivars (cvs.): “Picholine Marocaine” and “Dahbia”. In order to carry out embryogenesis induction, proximal cotyledons were cultured in modified olive medium (OMc) supplemented with 25 μM indole-3-butylic acid (IBA) and 2.5 μM 2-isopentenyladenine (2iP), while distal leaf fragments (somatic explants) were cultured in OMc supplemented with 4.56 µM zeatin riboside (ZR) and 10.25 µM 1-naphthaleneacetic acid (NAA). Regarding embryogenic potentials, the zygotic explants (cv. Picholine Marocaine: 43.39%; cv. Dahbia: 53.41%) were more regenerative than the somatic explants (cv. Picholine Marocaine: 13.05%; cv. Dahbia: 19.51%). The enzyme assay showed a higher POX activity in embryogenic calluses (ECs) than in nonembryogenic calluses (NECs) for the zygotic explants in both studied cultivars. When expressed as units per milligram of proteins (U mg⁻¹ proteins), the highest total POXs activities (soluble POXs + ionically wall-bound POXs) were found in the ECs derived from the zygotic explants; for cv. Dahbia, 65% of the enzyme activities came from the ionically wall-bound fractions. Polyacrylamide gel electrophoresis showed that the ECs of the highly active cv. Dahbia were characterized by highly active isoperoxidases that were revealed in four migration zones, particularly a doublet in the A4 zone (R_f 0.70–0.73) present in the ionically wall-bound POXs. The fast-moving anodic POXs of the ionically wall-bound fractions could be adopted as an early electrophoretic test to determine the embryogenesis capacities in olive tissue culture materials. As biochemical markers, the POX enzyme and its profile in fractions, i.e., as soluble POXs and ionically wall-bound POXs, can offer a valuable tool for improving the tissue culture of olive via somatic embryogenesis.

Arbuscular mycorrhizal fungi (AMF) play a key role in enhancing plant stress tolerance, nutrient uptake, and overall health, making them essential for sustainable agriculture. Their multifaceted contributions to the rhizosphere—through biofertilization, bioprotection, and biostimulation—have led to growing interest in their application. In recent years, in vitro mycorrhization has emerged as a promising approach for the rapid propagation of economically and ecologically important plant species, offering improved agronomic and physiological traits as well as increased resilience to environmental stressors. However, challenges remain in achieving consistent AMF-plant symbiosis under in vitro conditions across diverse species. This review highlights the potential of in vitro mycorrhization as a controlled system for investigating AMF interactions and their impact on plant development. Various in vitro mycorrhization systems are described and discussed, along with their applications in the mass production of AMF propagules and mycorrhizal plants, and their role in enhancing the acclimatization of micropropagated plantlets to ex vitro conditions. The role of in vitro mycorrhization as an effective tissue culture approach that integrates plant propagation with enhanced resilience to environmental stress is emphasized. The factors influencing the success of in vitro mycorrhization and strategies for the large-scale production of AMF propagules and mycorrhizal plants are explored. Although research in this area is still limited, existing studies underscore the potential of in vitro mycorrhization to enhance plant tolerance to abiotic and biotic stresses—an increasingly urgent goal in the context of climate change and global food security.